ما هو دليل الحنابلة والمالكية في تحديد إدراك صلاة الكسوف؟

According to the Malikis, the eclipse prayer consists of two cycles (rak'ahs), and the first bowing (rukū') in them is a sunnah, not a pillar. They consider a rak'ah to be caught by catching the second bowing, because it is the obligatory one. As for the Hanbalis, they believe that the first bowing is the essential one and the second is supplementary, and a rak'ah is not caught in their view except by catching the first bowing.

This is a matter of ijtihad (independent reasoning) for which there is no definitive text.